Special Issue "New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: 30 September 2019.

Special Issue Editor

Guest Editor
Prof. Dr. Yoko Hoshi

Department of Biomedical Optics, Hamamatsu University School of Medicine, Hamamatsu, Japan
Website | E-Mail
Interests: diffuse optical tomography; time-resolved spectroscopy; cognitive neuroscience; oxygen metabolism

Special Issue Information

Dear Colleagues,

In 1977, Jöbsis first described the in vivo application of near-infrared spectroscopy (NIRS), which is also called diffuse optical spectroscopy. NIRS was originally designed for clinical monitoring of tissue oxygenation, and it has also become a useful tool for neuroimaging studies (functional near-infrared spectroscopy, fNIRS). A wide range of NIRS instruments have been developed, including commonly commercially available instruments for continuous wave (CW) measurement based on the modified Beer–Lambert law (steady-state domain measurement). During the past 40 years, difficulties in selective and quantitative measurements of tissue hemoglobin have been central issues in the NIRS field. To overcome the problems with quantification, time-domain (TD) and frequency-domain (FD) measurements have been developed. TD measurement is the most promising approach, whereas compared with CW and FD measurements, TD measurement has been less frequently used due to large and expensive instruments with poor temporal resolution and limited dynamic range. Recently, however, the technology has advanced, and TD measurement is now increasingly implemented in research and practice in various clinical settings. This upcoming Special Issue aims to demonstrate the cutting edge of TD diffuse optical spectroscopy and imaging. It covers all aspects of TD measurement, including advances in hardware and instrumentation, methodology, theory of light propagation, and practical implementation.    

Prof. Dr. Yoko Hoshi
Guest Editor

Manuscript Submission Information

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Keywords

  • time-domain diffuse optical spectroscopy
  • time-domain diffuse optical imaging
  • time-domain fluorescence imaging
  • optical properties of biological tissue
  • quantification
  • time-domain radiative transfer equation
  • time-domain photon diffusion equation

Published Papers (9 papers)

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Research

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Open AccessArticle
Relationship of Total Hemoglobin in Subcutaneous Adipose Tissue with Whole-Body and Visceral Adiposity in Humans
Appl. Sci. 2019, 9(12), 2442; https://doi.org/10.3390/app9122442
Received: 6 April 2019 / Revised: 10 June 2019 / Accepted: 11 June 2019 / Published: 14 June 2019
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Abstract
High whole-body and visceral adiposity are risk factors that can cause metabolic diseases. We hypothesized that the total hemoglobin concentration (total-Hb) in abdominal subcutaneous adipose tissue (SATab), an indicator of white adipose tissue (WAT) vascularity, correlates negatively with risk factors for [...] Read more.
High whole-body and visceral adiposity are risk factors that can cause metabolic diseases. We hypothesized that the total hemoglobin concentration (total-Hb) in abdominal subcutaneous adipose tissue (SATab), an indicator of white adipose tissue (WAT) vascularity, correlates negatively with risk factors for developing metabolic diseases, such as whole-body and visceral adiposity. We tested the optical characteristics of abdominal tissue in 140 participants (45 men and 95 women) who were apparently healthy individuals with a median age of 39 years. They also had a median body fat percentage of 25.4%, a visceral fat area of 50.4 cm2, and a SATab thickness of 1.05 cm. These tests were conducted using near-infrared time-resolved spectroscopy (NIRTRS) with a 2-cm optode separation. To distinguish the segments of SATab (SegSAT) and the mixture of muscle and SATab (SegSAT+Mus), the threshold was analyzed using the slopes of (total-Hb) against the thickness of SATab using the least-squares mean method. According to the results from the logistic regression analysis, the percentage of body fat and visceral fat area remained significant predictors of the (total-Hb) (p = 0.005 and p = 0.043, respectively) in the data for SegSAT (no influence from the SATab thickness). We conclude that simple, rapid, and noninvasive NIRTRS-determined (total-Hb) in WAT could be a useful parameter for evaluating risk factors for metabolic diseases. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessArticle
A Versatile Setup for Time-Resolved Functional Near Infrared Spectroscopy Based on Fast-Gated Single-Photon Avalanche Diode and on Four-Wave Mixing Laser
Appl. Sci. 2019, 9(11), 2366; https://doi.org/10.3390/app9112366
Received: 15 April 2019 / Revised: 1 June 2019 / Accepted: 4 June 2019 / Published: 10 June 2019
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Abstract
In this paper, a time-domain fast gated near-infrared spectroscopy system is presented. The system is composed of a fiber-based laser providing two pulsed sources and two fast gated detectors. The system is characterized on phantoms and was tested in vivo, showing how the [...] Read more.
In this paper, a time-domain fast gated near-infrared spectroscopy system is presented. The system is composed of a fiber-based laser providing two pulsed sources and two fast gated detectors. The system is characterized on phantoms and was tested in vivo, showing how the gating approach can improve the contrast and contrast-to-noise-ratio for detection of absorption perturbation inside a diffusive medium, regardless of source-detector separation. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessArticle
Effects of Aging, Cognitive Dysfunction, Brain Atrophy on Hemoglobin Concentrations and Optical Pathlength at Rest in the Prefrontal Cortex: A Time-Resolved Spectroscopy Study
Appl. Sci. 2019, 9(11), 2209; https://doi.org/10.3390/app9112209
Received: 9 April 2019 / Revised: 20 May 2019 / Accepted: 20 May 2019 / Published: 29 May 2019
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Abstract
Background: In order to evaluate usefulness of a time-resolved spectroscopy (TRS) in screening test of cognitive dysfunction, we studied the effects of aging, cognitive dysfunction, brain atrophy on hemoglobin (Hb) concentrations and optical pathlengths (OPLs) in the prefrontal cortex (PFC) at rest, using [...] Read more.
Background: In order to evaluate usefulness of a time-resolved spectroscopy (TRS) in screening test of cognitive dysfunction, we studied the effects of aging, cognitive dysfunction, brain atrophy on hemoglobin (Hb) concentrations and optical pathlengths (OPLs) in the prefrontal cortex (PFC) at rest, using TRS. Methods: Employing TRS, we measured Hb concentrations and OPLs at rest in the PFC, and evaluated the relationship between the TRS parameters and cognitive function assessed by Mini-Mental State Examination (MMSE). In addition, we evaluated the relationship between the TRS parameters and the brain atrophy assessed by MRI. Results: We found positive correlations between MMSE scores and oxygen saturation (SO2), oxy-Hb in the PFC, suggesting that the greater the degree of PFC activity, the higher the cognitive function. In addition, we found the negative correlation between the subject’s age and SO2 and oxy-Hb in the PFC, suggesting that the older the subject, the lower the PFC activity at rest. Moreover, the OPLs in the right PFC negatively correlated with degree of brain atrophy evaluated by MRI, indicating that the shorter the OPL, greater degree of brain atrophy. Conclusions: TRS allowed us to evaluate the relation between the cerebral blood oxygenation (CBO) in the PFC at rest and cognitive function. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessArticle
Measurement of the Absolute Value of Cerebral Blood Volume and Optical Properties in Term Neonates Immediately after Birth Using Near-Infrared Time-Resolved Spectroscopy: A Preliminary Observation Study
Appl. Sci. 2019, 9(10), 2172; https://doi.org/10.3390/app9102172
Received: 5 April 2019 / Revised: 21 May 2019 / Accepted: 21 May 2019 / Published: 27 May 2019
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Abstract
The aim of this study was to use near-infrared time-resolved spectroscopy (TRS) to determine the absolute values of cerebral blood volume (CBV) and cerebral hemoglobin oxygen saturation (ScO2) during the immediate transition period in term neonates and the changes in optical [...] Read more.
The aim of this study was to use near-infrared time-resolved spectroscopy (TRS) to determine the absolute values of cerebral blood volume (CBV) and cerebral hemoglobin oxygen saturation (ScO2) during the immediate transition period in term neonates and the changes in optical properties such as the differential pathlength factor (DPF) and reduced scattering coefficient (μs’). CBV and ScO2 were measured using TRS during the first 15 min after birth by vaginal delivery in term neonates who did not need resuscitation. Within 2–3 min after birth, CBV showed various changes such as increases or decreases, followed by a gradual decrease until 15 min and then stability (mean (SD) mL/100 g brain: 2 min, 3.09 (0.74); 3 min, 3.01 (0.77); 5 min, 2.69 (0.77); 10 min, 2.40 (0.61), 15 min, 2.08 (0.47)). ScO2 showed a gradual increase, then kept increasing or became a stable reading. The DPF and μs’ values (mean (SD) at 762, 800, and 836 nm) were stable during the first 15 min after birth (DPF: 4.47 (0.38), 4.41 (0.32), and 4.06 (0.28)/cm; μs’: 6.54 (0.67), 5.82 (0.84), and 5.43 (0.95)/cm). Accordingly, we proved that TRS can stably measure cerebral hemodynamics, despite the dramatic physiological changes occurring at this time in the labor room. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessArticle
Compression Stockings Suppressed Reduced Muscle Blood Volume and Oxygenation Levels Induced by Persistent Sitting
Appl. Sci. 2019, 9(9), 1800; https://doi.org/10.3390/app9091800
Received: 4 March 2019 / Revised: 24 April 2019 / Accepted: 28 April 2019 / Published: 30 April 2019
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Abstract
This study quantitatively analyzed the effects of 3 h of constant sitting on skeletal muscle oxygenation in the lower extremities, using near-infrared time-resolved spectroscopy (NIRTRS). The effects of compression stockings were also evaluated. Eleven healthy men (age, 30.0 ± 6.7 years) [...] Read more.
This study quantitatively analyzed the effects of 3 h of constant sitting on skeletal muscle oxygenation in the lower extremities, using near-infrared time-resolved spectroscopy (NIRTRS). The effects of compression stockings were also evaluated. Eleven healthy men (age, 30.0 ± 6.7 years) maintained their knee joints at 90° flexion during 3 h of constant sitting and wore a compression stocking on either the right or left leg. The side the stocking was worn was chosen randomly. Subsequently, leg circumference and extracellular water were measured. After 3 h of sitting, both factors increased significantly in uncompressed limbs. Furthermore, intracellular water and muscle oxygenation had significantly decreased. In contrast, extracellular water had not increased in the limbs wearing compression stockings. Furthermore, the increased circumference of compressed limbs was significantly smaller than that of uncompressed limbs. Decreases in oxygenated hemoglobin and total hemoglobin were significantly smaller in compressed limbs than in uncompressed limbs (oxy-Hb; p = 0.021, total-Hb; p = 0.013). Three hours of sitting resulted in decreased intracellular water and increased extracellular water in the lower extremities, leading to reduced blood volume and oxygenation levels in skeletal muscle. Compression stockings successfully suppressed these negative effects. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessArticle
Comparison of Lipid and Water Contents by Time-domain Diffuse Optical Spectroscopy and Dual-energy Computed Tomography in Breast Cancer Patients
Appl. Sci. 2019, 9(7), 1482; https://doi.org/10.3390/app9071482
Received: 31 January 2019 / Revised: 3 April 2019 / Accepted: 4 April 2019 / Published: 9 April 2019
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Abstract
We previously compared time-domain diffuse optical spectroscopy (TD-DOS) with magnetic resonance imaging (MRI) using various water/lipid phantoms. However, it is difficult to conduct similar comparisons in the breast, because of measurement differences due to modality-dependent differences in posture. Dual-energy computed tomography (DECT) examination [...] Read more.
We previously compared time-domain diffuse optical spectroscopy (TD-DOS) with magnetic resonance imaging (MRI) using various water/lipid phantoms. However, it is difficult to conduct similar comparisons in the breast, because of measurement differences due to modality-dependent differences in posture. Dual-energy computed tomography (DECT) examination is performed in the same supine position as a TD-DOS measurement. Therefore, we first verified the accuracy of the measured fat fraction of fibroglandular tissue in the normal breast on DECT by comparing it with MRI in breast cancer patients (n = 28). Then, we compared lipid and water signals obtained in TD-DOS and DECT from normal and tumor-tissue regions (n = 16). The TD-DOS breast measurements were carried out using reflectance geometry with a source–detector separation of 3 cm. A semicircular region of interest (ROI), with a transverse diameter of 3 cm and a depth of 2 cm that included the breast surface, was set on the DECT image. Although the measurement area differed between the modalities, the correlation coefficients of lipid and water signals between TD-DOS and DECT were rs = 0.58 (p < 0.01) and rs = 0.90 (p < 0.01), respectively. These results indicate that TD-DOS captures the characteristics of the lipid and water contents of the breast. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessFeature PaperArticle
Early Therapeutic Prediction Based on Tumor Hemodynamic Response Imaging: Clinical Studies in Breast Cancer with Time-Resolved Diffuse Optical Spectroscopy
Appl. Sci. 2019, 9(1), 3; https://doi.org/10.3390/app9010003
Received: 22 October 2018 / Revised: 27 November 2018 / Accepted: 12 December 2018 / Published: 20 December 2018
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Abstract
This study reports data from three clinical studies using the time-resolved diffuse optical spectroscopy (TRS) system among breast cancer patients. The parameters of oxy-hemoglobin (O2Hb), deoxy-hemoglobin (HHb), total hemoglobin (tHb), and oxygen saturation (SO2) were evaluated using TRS, and [...] Read more.
This study reports data from three clinical studies using the time-resolved diffuse optical spectroscopy (TRS) system among breast cancer patients. The parameters of oxy-hemoglobin (O2Hb), deoxy-hemoglobin (HHb), total hemoglobin (tHb), and oxygen saturation (SO2) were evaluated using TRS, and its efficacy was tested in three trials. In trial 1, we recruited 118 patients with primary breast cancer to estimate the tumor detection rate. The cumulative detection rate was 62.7%, while that in T stage 0 was 31.3% and in T stage 1 was 44.7%. These were lower than those of T stage 2 (78.9%) and T stage 3 (100%). Next, we used TRS to monitor tumor hemodynamic response to neoadjuvant chemotherapy (n = 100) and found that pathological complete response (pCR) tumors had significantly lower tumor tHb than non-pCR tumors; a similar result was observed in estrogen receptor (ER)-negative tumors, but not in ER-positive tumors. The third trial monitored hemodynamic response to antiangiogenic therapy, bevacizumab (n = 28), and we demonstrated that sequential optical measurement of tumor SO2 might be useful for detecting acute hypoxia 1–3 days after bevacizumab initiation. Next, response monitoring of neoadjuvant endocrine therapy (n = 30) suggested that changes in tumor tHb during treatment can predict and distinguish between responsive and non-responsive tumors early in letrozole therapy. In conclusion, our results show that hemodynamic monitoring of tumors by TRS could pair the unique features of tumor physiology to drug therapy and contribute to patient-tailored medicine. We recently established a platform for performing TRS in patients with breast cancer. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Review

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Open AccessReview
Clinical Brain Monitoring with Time Domain NIRS: A Review and Future Perspectives
Appl. Sci. 2019, 9(8), 1612; https://doi.org/10.3390/app9081612
Received: 28 February 2019 / Revised: 28 March 2019 / Accepted: 1 April 2019 / Published: 18 April 2019
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Abstract
Near-infrared spectroscopy (NIRS) is an optical technique that can measure brain tissue oxygenation and haemodynamics in real-time and at the patient bedside allowing medical doctors to access important physiological information. However, despite this, the use of NIRS in a clinical environment is hindered [...] Read more.
Near-infrared spectroscopy (NIRS) is an optical technique that can measure brain tissue oxygenation and haemodynamics in real-time and at the patient bedside allowing medical doctors to access important physiological information. However, despite this, the use of NIRS in a clinical environment is hindered due to limitations, such as poor reproducibility, lack of depth sensitivity and poor brain-specificity. Time domain NIRS (or TD-NIRS) can resolve these issues and offer detailed information of the optical properties of the tissue, allowing better physiological information to be retrieved. This is achieved at the cost of increased instrument complexity, operation complexity and price. In this review, we focus on brain monitoring clinical applications of TD-NIRS. A total of 52 publications were identified, spanning the fields of neonatal imaging, stroke assessment, traumatic brain injury (TBI) assessment, brain death assessment, psychiatry, peroperative care, neuronal disorders assessment and communication with patient with locked-in syndrome. In all the publications, the advantages of the TD-NIRS measurement to (1) extract absolute values of haemoglobin concentration and tissue oxygen saturation, (2) assess the reduced scattering coefficient, and (3) separate between extra-cerebral and cerebral tissues, are highlighted; and emphasize the utility of TD-NIRS in a clinical context. In the last sections of this review, we explore the recent developments of TD-NIRS, in terms of instrumentation and methodologies that might impact and broaden its use in the hospital. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessFeature PaperReview
Time-Domain Near-Infrared Spectroscopy and Imaging: A Review
Appl. Sci. 2019, 9(6), 1127; https://doi.org/10.3390/app9061127
Received: 27 December 2018 / Revised: 2 March 2019 / Accepted: 5 March 2019 / Published: 17 March 2019
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Abstract
This article reviews the past and current statuses of time-domain near-infrared spectroscopy (TD-NIRS) and imaging. Although time-domain technology is not yet widely employed due to its drawbacks of being cumbersome, bulky, and very expensive compared to commercial continuous wave (CW) and frequency-domain (FD) [...] Read more.
This article reviews the past and current statuses of time-domain near-infrared spectroscopy (TD-NIRS) and imaging. Although time-domain technology is not yet widely employed due to its drawbacks of being cumbersome, bulky, and very expensive compared to commercial continuous wave (CW) and frequency-domain (FD) fNIRS systems, TD-NIRS has great advantages over CW and FD systems because time-resolved data measured by TD systems contain the richest information about optical properties inside measured objects. This article focuses on reviewing the theoretical background, advanced theories and methods, instruments, and studies on clinical applications for TD-NIRS including some clinical studies which used TD-NIRS systems. Major events in the development of TD-NIRS and imaging are identified and summarized in chronological tables and figures. Finally, prospects for TD-NIRS in the near future are briefly described. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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